Rupture lines in flexible packages

ABSTRACT

Method and apparatus for producing rupturable areas in thermoplastic film wherein said film is used to make closed flexible containers or packages that are easily ruptured for the release of contents contained therein. The apparatus is comprised of a male mold portion and a female mold portion having the film interposed therebetween. Application of heat and pressure to the film by the male and female mold portions cause the plastic film to extrude outwardly from the impression area thereby forming a weakened line or area in the film by selectively reducing the thickness thereof. The film is then formed into flexible packages having the rupture area in a selected position.

This is a continuation of application Ser. No. 578,132, filed May 16,1975, now abandoned.

The present invention relates to apparatus and method for producingcontrolled rupturable areas in thermoplastic film that is used in themanufacture of closed flexible containers or packages. Attempts havebeen made in the past to produce rupturable containers particularlymulti-compartment rupturable containers wherein one container isenclosed in another container for separating materials that are to bemixed at a later time. Difficulties have been encountered withrupturable containers, for example inability to rupture the innercontainer without rupturing the outer container; the requirement ofexcessive force to rupture the inner container; not having the innercontainer rupture in the proper place; and inability to make rupturablecontainers from non-heat sealable materials such as Mylar. Typical ofrupturable containers that have been produced are the type designed torupture along a heat sealed portion of an inner container and whereinthis is little control over the amount of rupture force necessary andlittle selection of the rupture line position.

The principal objects of the present invention are: to provide a methodand apparatus for producing rupturable areas in thermoplastic filmwherein the film can be formed into flexible rupturable packages thatovercome the above mentioned difficulties; to provide such a method andapparatus wherein the product or packages produced from the film haverupturable areas with predetermined rupture characteristics; to providesuch an apparatus and method that will make rupture areas in varioustypes of thermoplastic film including certain types that are notthermally sealable; to provide such an apparatus and method that willproduce rupture areas that will assure rupture in the desired area ofthe flexible container; to provide such an apparatus and method thatwill produce rupture areas in thermoplastic film at high operatingspeeds; to provide such an apparatus which includes means to controloperating parameters with resultant consistency in rupture strength ofthe rupture area; and to provide such apparatus that is economical tooperate and maintain, safe to use, efficient in operation, and welladapted for its intended purpose.

Other objects and advantages of this invention will become apparent fromthe following detailed description taken in connection with theaccompanying drawings wherein are set forth by way of illustration andexample certain embodiments of the present invention.

FIG. 1 is a perspective view of rupture line producing apparatusembodying this invention of the sequential feed type and having astraight male mold ridge pattern.

FIG. 2 is an enlarged sectional view taken on the lines 2--2, FIG. 1,but showing mold means in engagement with plastic film and illustratingcertain parts with highly exaggerated thicknesses.

FIG. 3 is an enlarged fragmentary view including the mold means of FIG.2, with portions broken away to show structural details at one endthereof.

FIG. 4 is a bottom view of a male portion of the mold means of FIG. 2but showing a modified ridge pattern.

FIG. 5 is a perspective view of continuous feed type rupture lineproducing apparatus.

FIG. 6 is an enlarged section view of the mold means taken along theline 6--6, FIG. 5 but showing the mold means in engagement with theplastic film and illustrating certain parts with highly exaggeratedthickness.

FIG. 7 is an elevational view of a male portion of the mold means ofFIG. 2 but showing a modified ridge pattern.

FIG. 8 is a section view of the rupture area in the plastic film withthe vertical dimension highly exaggerated.

FIG. 9 is an elevational view of a multi-compartment package.

FIG. 10 is a section view of the multi compartment package taken alongthe line 10--10, FIG. 9.

Referring more in detail to the drawings:

The reference numeral 1 designates generally an apparatus for producingrupture or weakened areas in plastic film. The apparatus 1 includes amold means comprised of a male mold portion 3 and a female mold portion4 mounted on a frame structure 5 wherein the mold portions 3 and 4 aremovable toward and away from each other and thermoplastic film 6 isinterposed therebetween. Heating means, described below, are in heattransfer relation with at least one of the male portion 3 and femaleportion 4 whereby both heat and force may be applied to thethermoplastic film 6 to form a decreased thickness area or impression,producing a weakend or rupture line therein. Preferably thethermoplastic film 6 is in the form of an elongate sheet intermittentlyfed between the male portion 3 and the female portion 4.

In the illustrated structure, the male portion 3 and the female portion4 are elongate members positioned in substantially parallel relationalong the length thereof. The female portion 4 is mounted on a table 8formed by the frame 5 and the male portion 3 is mounted on an elongatebrace 9 that is positioned above the table 8. Preferably, the brace 9 ismovable relative to the table 8 and has arms 10 secured to each endthereof which are pivotally mounted on upstanding supports 11 that aresecured to the table 8. A link 13 is secured to each of the arms 10 andis operatively connected to a force applying device such as an aircylinder 14 that is operable on command so as to move the male portion 3and the female portion 4 into engagement with opposite surfaces 16 and17 of the film 6, FIG. 2. The male portion 3 and the female portion 4have a male mold surface 12 and female mold surface 15 and cooperate toapply force and heat to the plastic film in selected areas therebycausing portions of the plastic film 6 to extrude and produce animpression or a decreased thickness area in the plastic film 6.Preferably the surfaces 12 and 15 have anit-stick qualities preventingadhesion of the plastic film 6 thereto.

In the form illustrated, the male poriton 3 is comprised of a resilientmember 20 that is suitably secured to the brace 9 such as by a channelmember 21 that has flange portions 22 that grippingly engage sideportions of the resilient member 20. The resilient member 20 has a lowersurface 24 with a protuberance or rib 25 thereon forming the surface 12which is engageable with the surface 16 of the plastic film 6. The rib25 may be one of various forms or shapes and as illustrated comprises awire 26 having a resilient coating 27 of material thereon such asTeflon. Preferably the rib 25 extends the length of the resilient member20 and has opposite ends thereof secured to means such as capstans (notshown) that are suitably secured to the brace member 9 and hold the rib25 in engagement with the resilient member 20, maintaining tension inthe wire 26. It is to be noted that selected areas along the resilientmember 20 may be absent of the rib 25 for a purpose later described.

The female portion 4 is suitably mounted on the table 8 wherein thesurface 15 is positioned adjacent and substantially parallel to thesurface 12. In the illustrated structure, the female portion 4 iscomprised of a base member 30 that is mounted on the table 8 and has anupper surface 31 that is covered by a layer of material 32 such asTeflon impregnated fiberglass. Preferably the female portion 4 isprovided with heating means and as illustrated a heating element 34overlies a portion of the layer of material 32 and extends substantiallythe length of the base member 30. The heating element 34 preferably isan electrical resistance type heater such as hard nichrome and isconnected to an electric power supply (not shown) by electricalconductors 33 and the material 32 is an electrical insulator. Theheating element 34 extends along the length of the base member 30 and issuitably held in position on the layer of material 32.

Preferably, the heating element 34 is maintained in a tensionedcondition to prevent buckling or warpage when expanding and contractingdue to changes in temperature. As illustrated in FIG. 3, the base member30 has a notch 36 at each end thereof for receiving a spring loadedtensioning block 37 therein. The block 37 has a pin 38 extendingtherefrom surrounded by a spring member 39. The pin 38 extends into abore 41 in the base member 30 wherein the spring 39 is positionedbetween the block 37 and a surface of the notch 36. The heater 34 hasbrackets 42 secured to each end thereof with each of the brackets beingsuitably secured to a respective block member 37 such as with screwfasteners 43. Preferably the blocks 37 are of an electricallynon-conductive material thereby preventing conduction of electricityfrom the heating element 34 to the base member 30. The block members 37are retained in the notches 36 by abutment forming members 45 that areeach secured to a respective end of the base member 30 therebymaintaining tension in the heater 34 and compensating for expansion andcontraction thereof due to temperature changes.

A layer 50 of resilient material such as teflon impregnated fiberglassis secured to the base member 30 and overlies the heater 34, providingelectrical insulation for the heater 34 and a resilient covering.Preferably a second layer 52 overlies and is secured to the layer 50 andis of a resilient material such as Teflon impregnated fiberglass and isself-adhering for securing same to the layer 50. The layer 52 provides athicker resilient covering over the heater 34 and because of itsadhesive engagement it is easily replaceable when it becomes worn. Thelayers 32, 50, and 52, the heater 34 and the plastic film 6 are each inthe order of 0.005 inch to 0.010 inch in thickness but are highlyexaggerated in the drawings for clarity.

In operation, the plastic film 6 is interposed between the surfaces 12and 15 and pressurized air is supplied to the cylinder 14, moving thesurfaces 12 and 15 into engagement with the surfaces 16 and 17respectively. Heat supplied by the heater 34 is transferred through thelayers 50 and 52 to the plastic film 6 and the force applied causes theplastic film 6 to extrude forming an impression or reduced thicknessline or area 54 as is best seen in FIG. 8 in which the thickness of theplastic film 6 is highly exaggerated. The force applied by the surface12 produces resilient or elastic deformation in the layers 50 and 52whereby they conform generally in shape to the rib 25, producing aportion 55 in the film 6 which protrudes slightly outwardly from thesurface 17.

It is to be noted that the lower surface 24 and the rib 25 may be one ofvarious shapes or contours and as illustrated the rib 25 has a generallyround cross section and the lower surface 24 is nonplanar and hasgrooves 59 on opposite sides of the rib 25. The grooves 59 form ridges50' that are seen as sharp edge terminations of the weakened area 54 onopposite sides of the portion 55 when viewed in actual size, but whenenlarged as illustrated in the example of FIG. 8, are seen to havecontoured lateral surfaces smoothly blending into the portion 55 whichforms a web integral with the film 6. Preferably the heat supplied bythe heater 34 is produced by a current pulse of controlled duration andis controlled by suitable pulse forming means 56. Such pulse isdesirably supplied during the period of time when the surfaces 12 and 15are in contact with the plastic film 6. Before the male portion 3 ismoved to a non-engaging position the heater is deactivated so as toallow cooling of the plastic film 6. To speed up the cooling process achannel 51 can be provided in the base member 30 whereby coolant 53 inthe channel 51 acts as a heat sink for rapid cooling of the surface 15.A control unit 57 has suitable control devices (not shown) mountedtherein and operable to control the temperature of the heating element34, the duration of time that the male member 3 is in engagement withthe film 6 and the force applied to the film 6. Adjustment of thesecontrol devices will determine the thickness of the film 6 at theimpression 54 and consequently the amount of force required to rupturethe plastic film 6 at the weakened line area 54.

Although the rib 25 discussed in connection with FIGS. 1 and 2 isstraight, it is to be noted that the rib can be one of several differentconfigurations with a preferred configuration being illustrated in FIG.4. The structure as illustrated in FIG. 4 includes a generallysinusoidal shaped rib 58 having grooves 58' on opposite sides thereofsimilar to the grooves 59, that will produce a corresponding shape ofweakened line or area in the plastic film 6. Also, portions of the rib25 may be eliminated for producing alternating weakened and strong areasalong the plastic film 6.

FIGS. 5, 6, and 7 illustrate a modified form of the present inventionwherein the reference numeral 60 designates generally an apparatus forproducing the rupture lines or areas in plastic film continuously by useof a roller rather than in sequential steps. The apparatus 60 includes amold means comprised of a cylindrical male mold portion 62 and astationary female mold portion 63 mounted on a frame structure 64 forselective pressure engagement together and having thermoplastic filminterposed therebetween. The male portion 62 is rotatable and the femaleportion 63 has low friction characteristics whereby the plastic film 6can be continuously fed therebetween. Heating means are in heat transferrelation to at least one of the male portion 62 and the female portion63 whereby heat and force may be applied to the film 6 to form thedecreased thickness area or impression in the thermoplastic filmdiscussed above.

In the illustrated structure, the male portion 62 and the female portion63 are mounted on a table member 66 formed by a frame structure 64,preferably with the portion 62 being positioned above the portion 63.The portion 62, in the form shown, includes a roller member 67 mountedon a shaft 68 that is suitable driven by power means 69, such as anelectric motor that is operatively connected to the shaft 68. The rollermember 67 and the shaft 68 are selectively movable toward and away fromthe portion 63 and has means associated therewith for applying aselected force to the plastic film 6. As illustrated, air cylinders 70are connected to the shaft 68 at opposite ends thereof and are operableon command to raise and lower the male portion 62 relative to the femaleportion 63 and by regulation of the air pressure to the cylinders 70,the amount of force between the male portion 62 and the female portion63 can be adjusted. The shaft 68 has the opposite ends thereof rotatablymounted in bearing members 71 that in turn are suitably movably mountedin generally upright support members 72. The roller member 67 isprovided with a protuberance or rib 73 projecting radially outwardly ofthe roller member 67, preferably having grooves 73' on opposite sidesthereof to form the ridges 59'. The rib 73 engages the plastic film 6and urges the plastic film 6 to extrude away from same under theinfluence of heat and force as previously described. Preferably, theroller member 67 and the rib 73 have anti-stick qualities to preventadhesion with the plastic film 6.

The female portion 63 is similar in construction and operation to thefemale portion 4 wherein the heating means includes an electricalresistance heater 74 supported by a base member 75 that is secured tothe table 66. A layer 76 of electrically non-conductive material, suchas Teflon impregnated fiberglass, is secured to the base member 75 andis positioned between same and the heater 74 thereby electricallyinsulating the heater 74 from the base member 75. One or more layers ofmaterial, such as Teflon impregnated fiberglass, overlie the heater 74providing a resilient covering therefor. The layers 77 and 78 aresuitably secured to the base member 75 and preferably the layer 77 has aself-adhering surface that adheres to the layer 78. The surface 79 ofthe layer 77 that engages the plastic film 6 has anti-stick qualitiesfor preventing adhesion to the plastic film 6. The ends of the femaleportion 63 have sloping portions to facilitate movement of the plasticfilm 6 thereover. The heater 74 is maintained in a tensioned conditionin a method similar the heater 34 discussed above.

In the illustrated structure, the roller member 67 has an outerperiphery or surface 80 with the rib 73 extending outwardly therefrom.It is to be noted that the rib 73 may be one of various forms and asillustrated in FIG. 6, is an annular rib or ring extendingcircumferentially around the roller 67. FIG. 7 illustrates a modifiedform of roller rib or protuberance designated 81 which is in asinusoidal shape that extends circumferentially around the roller 67 andhas grooves 81' on opposite side thereof similar to the grooves 73'.Also, if desired, portions, of the ribs 73 and 81 may be eliminated soas to form alternating strong areas and weak areas in the plastic film6.

In operation the plastic film is fed between the male portion 62 and thefemale portion 63 and is moved therebetween by rotation of the maleportion 62. Guide means, such as a roller 82 having collars 83 mountedthereon can be positioned upstream of the mold means guiding the plasticfilm 6 to the mold means. The male portion 62 is raised by actuation ofthe cylinders 70 to facilitate interposing plastic film 6 between themale portion 62 and the female portion 63. Driving or pulling means suchas power driven rollers 90 are provided to engage the plastic film 6 tohelp in inducing movement of the plastic film 6 between the male portion62 and the female portion 63. The speed of the rollers 90 issynchronized to the speed of the male portion 63 and can be driven bythe motor 69. Preferably heat is continuously supplied to the film 6 bythe heater 74 and the cooperation of the force supplied by the maleportion 62 and the heat supplied by the heater 74 produce a weakened orrupture area in the film 6 by the plastic extruding away from the rib73. Preferably the temperature of the heater 74, the force applied bythe male portion 62 and the operating speed are adjustable by controlmeans mounted in a control panel 84.

FIGS. 9 and 10 illustrate a multi-compartment package designatedgenerally by the reference numeral 85 comprised of an inner container 86and an outer container 87. The outer container 87 is formed by folding asheet of plastic film as at 88 and heat sealing portions of the oppositesides as at 89. The inner container 86 is fabricated using the plasticfilm 6 having the weakened area 54 positioned as at 91 and having theopposite sides 92 and the side 93 each sealed, such as by heat sealing,for enclosing the contents 94 therein in a sealed or closed package.Materials 95 are placed in the container 87 and then the package 86 isplaced in the package 87 and as illustrated, is heat-sealed betweenopposite layers of the package 87 as at 96, thereby forming amulti-compartment package having two materials contained thereinisolated from one another. Such packages are useful for containingmaterials such as adhesives, food substances and the like which are notto be mixed until used. To mix the contents 94 and 95 of the packages 86and 87 respectively, force is applied to the package 86 from theexterior of the package 87 thereby causing the package 86 to rupturealong the rupture line or area 54 due to increased pressure in thepackage 86.

It is to be understood that while I have illustrated and describedcertain forms of my invention, it is not to be limited to the specificforms or arrangement of parts herein described and shown except insofaras such limitations are included in the following claims.

What I claim and desire to secure by Letters Patent is:
 1. A containercomprising:(a) a pressure rupturable sealed bag containing material andconstructed of a flexible thermoplastic sheet film wall having an uppersurface and a lower surface, said bag having a heat sealed side; (b) arupture line extending a substantial distance along an integral extentof said sheet film wall and to said heat sealed side, said rupture linebeing characterized as an elongated groove having contoured lateralsurfaces smoothly blending into said upper surface and into a webportion integral with said sheet film wall, said web portion having across-sectional thickness substantially reduced and weakened in tensilestrength from that of the non-groove portions of said sheet film walland protruding outwardly from said lower surface, said web portionproviding a resistance against rupture less than the non-groove portionsof said sheet film wall, (c) whereby application of a predeterminedinternal pressure to said container will cause the container to rupturealong said rupture line for release of the material therein.
 2. Thecontainer as set forth in claim 1 wherein:(a) said bag has opposite heatsealed sides and said rupture line extends to said opposite heat sealedsides.
 3. The container as set forth in claim 1 wherein:(a) said ruptureline includes ridges protruding form said upper surface and smoothlyblending thereinto.
 4. In a flexible container:(a) a bag having a wallof flexible thermoplastic sheet film and opposite heat sealed sides; (b)a rupture line in said wall and extending to said opposite sides, saidrupture line comprising an elongated groove having contoured lateralsurfaces smoothly blending into one surface of said sheet film wall andinto a web portion integral with said sheet film wall, said web portionbeing of cross-sectional thickness substantially less than and weakenedin tensile strength from the non-groove portions of said sheet film walland protruding outwardly from one surface of said sheet film wall andproviding a resistance against internal pressure produced rupture lessthan the non-groove portions of said sheet film wall.